Novel ternary semiconducting materials



United States Patent 3,454,370 NOVEL TERNARY SEMICONDUCTING MATERIALSGeorge Augustus 'Castellion, Stamford, Conn., assignor to AmericanCyanamid Company, Stamford, Conn., a corporation of Maine No Drawing.Filed May 26, 1966, Ser. No. 553,010 Int. Cl. C01b 29/00; H01b 1/06;H01v 1/20 US. Cl. 23-315 7 Claims ABSTRACT OF THE DISCLOSURE There isprovided a semiconducting, single phase composition of matter such asZnFe Sb ZnCo Sb Zn CoSb MgMn Sb MgCo Sb and FeCd As useful inphotocells, thermocouples and rectifiers.

The present invention relates to novel ternary semiconductingcompositions of matter. More particularly, it relates to novel ternarysemiconducting, single phase compositions of matter and has as itsprincipal object their use in solid state semiconductor devices.

Ternary or three elemental component semiconducting compositions ofmatter are well known. They find utility in solid state conductordevices, such as, for intsance, rectifiers, photocells, photoconductors,thermocouples and thermoelectric generators. However, many of theternary semiconducting compounds are unfortunatel found in a pluralityof phases. As such, these semiconducting ma terials are substantiallyineflicient as thermoelectric compounds used in, for instance,generators. It is further known that admixtures of metals so as to alloythem does not necessarily result in a single phase. Frequently, the newalloy does result in a plurality of phases.

It has been found unexpectedly that semiconducting compounds may bereadily formed so as to produce crystals of a single phase. Suchcompounds can be represented by the formula:

3-m m 2 or A3 D AS where A is an element, such as zinc, manganese,magnesium or iron and D is an element, such as iron, cobalt, manganeseor cadmium, m is an integer from 1 to 2 and wherein A and D aredissimilar elements. The compounds prepared by the process of theinvention are found to be not only semiconducting, but are found topossess a crystalline habit of a single phase.

In general, the ternary compounds of the present invention can beprepared by comminuting into diminutive particles the elements definedby the above noted formula. In this form, the elements can be easilyhandled. For optimum operation, the particle size of the elements shouldnot exceed about ten millimeters in diameter. Initially, the elementsare mixed in the required stoichiometric amounts, then loaded into acrucible which is evacuated, sealed and subjected to elevatedtemperatures. This is usually done by placing the crucible containingthe mixed elements into a furnace and heating the crucible and contentsto a temperature above the melting point of the material or compositionof matter to be prepared. Temperatures above about 700 C. will berequired to accomplish this end. Depending on the temperature employed,the time required to fuse the elements commencing at room temperatureranges from about thirty minutes to three hours. For most preparations,a time of about one hour appears to be the upper limit.

The temperatures employed are sufficient as to liquefy the elementspresent. In this state, the elements are intimately mixed by rocking thecrucible-containing furnace. Uniformity of product is thereby achieved.Thereafter, the contents in the crucible are cooled at rates rangingfrom approximately 2 C. to 20 C. per hour and this rate of cooling iscontinued until a temperature of about 400 C. is reached. At this point,the cooling rate is increased to from C. to C. per hour. Utilizing thistechnique, which is simpler than the crystal pulling technique normallyemployed in the art, it has been found that single crystal growth isachieved.

The semiconducting compounds formed by the process of the invention aresubjected to several tests to determine their electrical resistance aswell as the Seebeck coefi'icient. The latter terms are defined withparticularity in United States Letters Patent No. 3,211,517 which isincorporated herein by reference. In each examination of the productsresulting from the process of the invention, they exhibit goodsemiconducting properties.

In order to illustrate the present invention, the following examples arepresented merely by way of illustration and are not to be taken as beinglimitative of the invention.

Example 1 Stoichiometric quantities of zinc, iron and antimony whichcorrespond to the compound ZnFe Sb are admixed in the following manner:

A mixture of 2.176 2 grams of zinc and 3.7180 grams of iron areincorporated in a crucible of quartz tubing and the latter is evacuatedto a pressure of less than 1x10- mm. Hg. Thereafter, 8.1057 grams ofantimony under a nitrogen atmosphere are loaded into a side arm of thequartz tubing and the crucible is further evacuated to a pressure ofless than 1 10- mm. Hg.

The crucible and contents are then sealed and placed in a holder in aconventional resistance furnace. The furnace is equipped with a rockingdevice so as to permit the crucible and contents to be uniformlyadmixed. During heating to a temperature of about 1000 C., the furace iscontinuously rocked. When the latter temperature is attained, it ismaintained for an additional 3 hours during which time rocking of thefurnace is permitted to occur. Thereafter, the power to the furnace isreduced and the rocking is terminated so as to permit the contents inthe furnace to gradually cool at a steady rate from about 850 C. toabout 400 C. over a period of about 1% days. Thereafter, all the powerto the furnace is shut off and the furnace is allowed to cool to roomtemperature.

The contents in the crucible are removed and the resultant productrecovered is examined microscopically as well as being subjected toX-ray analysis. The product is found to be of a single phase andpossesses a resistance of 1 l0 ohm-centimeter and a Seebeck coetficientof 6.5 microvolts/ C. It is also found to possess good thermoelectricproperties.

Example 2.

Preparation of the compound ZnCo Sb Repeating the procedure of Example 1in every detail except that 3.8670 grams of cobalt, 2.1445 grams of zincand 7.9884 grams of antimony are admixed as elements, on X-ray analysis.Further, resultant compound ZnCo Sb is found to possess a resistance of1.0 10"' ohm-centimeter and a Seebeck coetficient equal to 11.2microvolts/ C.

Example 3 Prepare-d of the compound MnMg Sb The procedure of Example 1is repeated in every detail except that 2.2159 grams of manganese,1.9618 grams of magnesium and 9.8222 grams of antimony are admixed.Resultant compound is found to be of a single phase and possesses aresistance of 2.0)(10- ohm-centimeter.

Example 4 Example 5 Preparation of the compound MgMn Sb There areadmixed 0.9014 grams of magnesium, 4.0726 grams of maganese and 9.0259grams of antimony in accordance with the procedure of Example 1 above.Resultant product is found to possess a resistivity of 8.0 1Oohm-centimeter and on X-ray analysis is found to be of a single phase.

Example 6 Preparation of the compound MgCo Sb r The procedure of Example5 is repeated in every detail except that 0.8827 grams of magnesium,4.2785 grams of cobalt and 8.8387 grams of antimony are admixed. As inExample 5, resultant product is found to be of a single phase andpossesses a resistivity equal to 2.0 ohmcentimeter.

Example 7 Preparation of the compound F6Cd AS Repeating the procedure ofExample 1 in every detail except that 1.9460 grams of iron, 7.8329 gramsof cadmium and 5.2210 grams of arsenic are admixed, resultant product:FeCd As is formed. This product is found to possess a resistivity of3.2x 10- ohm-centimeter and a Seebeck coeificient equal to 29microvolts/ C. On X-ray analysis, it is found unequivocally to be of asingle phase.

What is claimed is:

1. A semiconducting, single phase composition of matter selected fromthe group consisting of ZnFe Sb ZnCo Sb ZII COS'bg, MgMl'lgsbg, MgCO Sband FCCdgASz.

2. The compound according to claim 1: ZnFe sb 3. The compound accordingto claim 1: ZnCo Sb 4. The compound according to claim 1: Zn CoSb 5. Thecompound according to claim 1: MgMn Sb 6. The compound according toclaim 1: MgCo Sb 7. The compound according to claim 1: PeCd AsReferences Cited UNITED STATES PATENTS 3,211,517 10/1965 CastelliOn252-62.3 X

OTHER REFERENCES Juza et al., Chemical Abstracts, vol. 61, p. 12733(1964).

Kasaya et al., Chemical Abstract, vol. 61, p. 15511 (1964).

TOBIAS E. LEVOW, Primary Examiner.

I. COOPER, Assistant Examiner.

US. CI. X.R.

-l22, 134; l36240; 25262.5l, 62.3, 501, 518, 519, 521

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,454,370 July 8, 1969 George Augustus Castellion It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 2, line 38, "furace" should read furnace line 61, "on X-rayanalysis." should read it is found that a single phase crystal structureis obtained on X-ray analysis. line 66, "Prepared" should readPreparation Column 3, line 15 "maganese should read manganese Signed andsealed this 21st day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

